A control system for controlling the power provided to a power-receiving load is traditionally produced and deployed on a discrete component basis. Discrete components are selected and combined for the particular application or receiving load.
FIG. 1 illustrates a typical exemplary power control arrangement composed of a variety of discrete components. These can include a control system 102 with an associated control sensor 104, an input 106 for receiving power from a power source 108, a contactor 110 for receiving the power from the power source 108, a limit 112 with an associated limit sensor 114, a fuse 116, a power switch 118 (shown as a solid state relay), and a power load 120 (shown as a heating element). As illustrated, each of the various discrete components is combined and hard-wired to meet the needs of a particular user process control application constituting a power control system 100. As indicated in FIG. 1, for this typical thermal loop power control application, the combination of discrete components for a single power loop requires 7 discrete components 102, 104, 110, 112, 114, 116, and 118, with 16 wires 122A-H and 24 wiring connections, two for each of 16 wires 122A-H, and labeled, for example as 124A and 124B, for the two wires 122A. However, other discrete components can also be included such as a timer, a pressure sensing component, a power monitor, etc. (none of which are shown in FIG. 1). The addition of each of these components will often require 2 wires 122 and possibly 4 connections 124 to terminate both ends of each wire and can require the rewiring of previous wires in order to reconfigure the wiring between the various components.
FIG. 2 illustrates another example of a typical power control arrangement 200 for controlling power for a thermal loop application. As shown, the control 102 can include a user interface 202 and controller 204 and have 6 connections 124 to 6 wires 122. A limit contactor 110 can be positioned between a power supply bus 206 that is coupled to a power supply 108 (not shown in FIG. 2) and then wired to a semiconductor fuse 116 such as a fast blow fuse. The fuse 116 provides a fusible connection to a power switch 118 that can be any type of power switch, but is often a semiconductor-based switch such as solid state relay (SSR), a TRIAC, or a silicon controller rectifier (SCR), by way of example. The power switch 118 provides power to a power load 120 such as a heater for heating a user application. A process or application sensor 104 senses the temperature of the heater 120 in the user application and provides feedback to the controller 204 for feedback control of the powering of the power load 120, such as a heater. Additionally, as discussed above, the limit contactor 110 receives input from a limit component 112 that includes a limit sensor 114. The limit sensor 114 is also located in proximity to the heater 120. The limit system comprised of the limit contactor 110, the limit component 112, and the limit sensor 114, monitors the operation of the heater 120 to protect the heating element of the heater 120 from destruction, failure or impairment. The limit component 112 receives power from the power bus 206 through a set of device fuses 208. The limit component 112 determines when the limit sensor 114 has detected a heater condition and signals to the limit contactor 110 over a separate wire, to initiate a limit action in the limit contactor 110, thereby preventing power from passing to the power switch 118 and therefore to the heater 120. As is also indicated in FIG. 2, each discrete component within the power control system 200 requires separate wiring 122 and numerous connections 124. Additionally, such wiring 122 and discrete component installations are often confusing to installers and wiring mistakes often result. Common mistakes made during installation include incorrect termination of leads to terminals resulting in circuit shorting or opens, poor compression of terminals to leads resulting in potential high temperatures at terminals, electrical magnetic interference with other components, or electromagnetic emissions.
As shown in FIG. 3, other common discrete components also include current transformers 302 or sensors or other measurement devices for measuring one or more characteristics of a power control user application. As shown in FIGS. 3A and 3B, one or more current transformers 302 can be positioned in the power supply line 304 from the power switch 118 to the heater power load 120 to sense current supplied to the heating element. Each current transformer 302 measures a current 306 in the power supply line 304 which is provided to a current transformer controller (not shown) which is yet another discrete component that requires installation, wiring and connections for installation into the user application. In some applications, this wiring requires the breaking of the power line 304 to introduce the current transformer 302 resulting in another opportunity for wiring mistakes.
Similarly, FIG. 4 illustrates another discrete component control system 400, having a control switch 118, such as a relay, is electrically located between the power load 120 and the contactor 110. The control relay 118 receives a control signal 402 from the controller 102 over a separately wired control lead 404. The control relay 118 operates in response to a control signal 402 from the controller 102 to provide power to the contactor 110 and therefore to the power load 120. Again, additional discrete components and specialized wiring are typically required for another user application.
Generally, typical power control installations require specialized selection of the discrete components, customized mounting and wiring for each component and feature, and multiple connections. Additionally, any changes, additions, modifications, and replacements require disconnection and reconnection of various wire leads, yet again increasing the opportunity for wiring mistakes.
As such, existing power control implementations and installations are often complex and costly to install. Such complexity and costs limit their application or limit the functionality included in a particular user application. For example, a limit control for over-voltage or a power monitoring component are not included in many applications when not required by a regulation due to the required added complexity and/or installed cost.